A study on determination of the surface echo top for an space-borne precipitation raday by suing digital elevation map

利用数字高程图确定星载降水辐射地面回波顶的研究

基本信息

批准号：
14550425
负责人：
AWAKA Jun
金额：
$ 0.96万
依托单位：
Hokkaido Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14550425/
关键词：
TRMM Precipitation Radar Surface echo Digital elevation map

项目摘要

Observation of rain from space is indispensable for out understanding of climate change, which is related to global warming; in particular, observation of rain by a space-borne radar is very important because the radar directly measure the 3D-structure of rain qualitatively with high precision. In the case of observation of rain by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), however, a strong surface echo can be misjudged as a strong rain echo over high mountain regions such as Tibet and Andes in a very rare cases, which remains to be an engineering issue though the frequency of the occurrence of such a misjudgment is very low. The goal of this study is to separate the rain echo and the surface echo in high precision; to achieve this goal, we need a reliable surface elevation map. Hence, we have generated a digital elevation map by using the TRMM PR data.After a preliminary study in FY2002, we concluded that we should generate a surface elevation map with a … More 2km x 2km grid. In FY2002 and FY2003, we have generated the surface elevation map using the TRMM PR data of Feb. 1998 and Sept. 1998. We have noticed that less than about one month of data covers the entire observation latitude range if we use the PR data of all the 49 antenna beam directions. In FY2004, we have compared thus obtained surface elevation map with SRTM30(Shuttle Radar Topography Mission digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds (approximately 1 km)), which is claimed to be the most accurate 1 km DEM.In and around Mt.Fuji, SRTM30 shows a large variation of elevation, and some elevations higher than 8500m, which are close to that of mountain top, but the SRTM PR surface elevation map is smooth and tends to trace the bottom line of SRTM30 in this area. This fact implies that the elevation data of SRTM30 is not an average of 1km x 1km grid but a peak in each grid.For the separation of rain echo and surface echo, two-steps approach is needed: one is the determination of the position of surface echo peak, and the other is the determination the surface echo top. For the determination of the position of surface echo peak, the use of the TRMM PR elevation map is useful. For the determination of the surface echo top, however, the use of SRTM30 is promising because we need information about the variability of elevation in the antenna beam area which seems to be provided by SRTM30. There is a possibility, however, that the use of SRTM30 alone maybe sufficient if we use median value of elevation in the antenna beam area. An issue is apply our results to the current TRMM PR standard algorithm. Less

从太空观测降雨对于了解气候变化是必不可少的，特别是与全球变暖有关，星载雷达观测降雨非常重要，因为雷达直接定性测量降雨的 3D 结构；然而，在热带雨量测量任务（TRMM）降水雷达（PR）观测降雨时，强地面回波可能被误判为西藏等高山地区的强雨回波。和安第斯山脉是一种非常罕见的情况，尽管这种误判发生的频率很低，但这仍然是一个工程问题。本研究的目标是高精度地分离降雨回波和地面回波；为了实现这个目标，我们需要一张可靠的地表高程图，因此，我们利用TRMM PR数据生成了一张数字高程图。经过2002财年的初步研究，我们得出的结论是，我们应该生成一张… 更多 2km x 的地表高程图。 2公里网格。 2002财年和2003财年，我们使用1998年2月和1998年9月的TRMM PR数据生成了地表高程图。我们注意到，如果使用1998年2月和1998年9月的PR数据，不到一个月的数据就覆盖了整个观测纬度范围。 2004财年，我们将由此获得的表面高程图与SRTM30（航天飞机雷达地形任务数字高程模型（DEM））进行了比较。水平网格间距为30角秒（约1公里）），号称是最精确的1公里DEM。在富士山及其周边地区，SRTM30显示高程变化较大，部分高程高于8500m，这使得接近山顶，但 SRTM PR 表面高程图是平滑的，并且倾向于追踪该区域 SRTM30 的底线，这一事实意味着 SRTM PR 的高程数据。 SRTM30不是1km x 1km网格的平均值，而是每个网格中的峰值。对于雨回波和地面回波的分离，需要分两步进行：一是确定地面回波峰值的位置，二是确定地面回波峰值的位置。确定表面回波峰值对于确定表面回波峰值的位置，使用 TRMM PR 高程图是有用的，但是对于确定表面回波峰值，使用 SRTM30 是有希望的，因为我们需要信息。关于可变性天线波束区域的仰角似乎是由 SRTM30 提供的，但是，如果我们使用天线波束区域的仰角中值，那么单独使用 SRTM30 可能就足够了。当前 TRMM PR 标准算法。